Module Name: src
Committed By: pgoyette
Date: Wed Aug 23 22:27:55 UTC 2017
Modified Files:
src/share/man/man9: locking.9
Log Message:
Add locking(9) and psref(9) summaries to locking(9).
PR misc/52504
XXX Pull-up to -8 ?
To generate a diff of this commit:
cvs rdiff -u -r1.5 -r1.6 src/share/man/man9/locking.9
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/share/man/man9/locking.9
diff -u src/share/man/man9/locking.9:1.5 src/share/man/man9/locking.9:1.6
--- src/share/man/man9/locking.9:1.5 Sun Apr 16 07:05:24 2017
+++ src/share/man/man9/locking.9 Wed Aug 23 22:27:55 2017
@@ -1,4 +1,4 @@
-.\" $NetBSD: locking.9,v 1.5 2017/04/16 07:05:24 wiz Exp $
+.\" $NetBSD: locking.9,v 1.6 2017/08/23 22:27:55 pgoyette Exp $
.\"
.\" Copyright (c) 2015 The NetBSD Foundation, Inc.
.\" All rights reserved.
@@ -212,6 +212,36 @@ The read operations may happen from soft
.Pp
See
.Xr pserialize 9 .
+.Ss Passive reference mechanism
+Passive references allow CPUs to cheaply acquire and release passive
+references to a resource, which guarantee the resource will not be
+destroyed until the reference is released. Acquiring and releasing
+passive references requires no interprocessor synchronization, except
+when the resource is pending destruction.
+.Pp
+See
+.Xr psref 9 .
+.Ss Localcount mechanism
+Localcounts are used in the kernel to implement a medium-weight reference
+counting mechanism. During normal operations, localcounts do not need
+the interprocessor synchronization associated with
+.Xr atomic_ops 3
+atomic memory operations, and (unlike
+.Xr psref 9 )
+localcount references can be held across sleeps and can migrate between
+CPUs. Draining a localcount requires more expensive interprocessor
+synchronization than
+.Xr atomic_ops 3
+(similar to
+.Xr psref 9 ) .
+And localcount references require eight bytes of memory per object per-CPU,
+significantly more than
+.Xr atomic_ops 3
+and almost always more than
+.Xr psref 9 .
+.Pp
+See
+.Xr localcount 9 .
.Ss Simple do-it-in-thread-context framework
The workqueue utility routines are provided to defer work which is needed to be
processed in a thread context.
@@ -236,6 +266,8 @@ can be used to protect shared resources
.It Xr spl 9 Ta yes Ta no Ta no
.It Xr splraiseipl 9 Ta yes Ta no Ta no
.It Xr pserialize 9 Ta yes Ta yes Ta no
+.It Xr psref 9 Ta yes Ta yes Ta no
+.It Xr localcount 9 Ta yes Ta yes Ta no
.It Xr workqueue 9 Ta yes Ta yes Ta yes
.El
.Sh SEE ALSO
